This invention is an apparatus and method useful for dispensing a predetermined weight of liquid. The invention is particularly useful in an apparatus for rapidly filling containers to a predetermined weight with a liquid which is obtained at variable temperatures throughout the year. The invention finds use in an apparatus for rapidly filling containers with expensive liquids.
Large amounts of liquids are sold by weight. However, it is much easier to dispense liquid by volumetric measurement. If the temperature of the liquid is not considered, large deviations in the weight of liquid contained in a given volume occur. For example, the weight of five gallons of an organic liquid can vary as much as 1 to 11/2 pounds over a temperature range of about 100F.degree..
To accurately fill containers with a given weight of liquid, the containers are usually filled by weight. To fill a container by weight, the container must first be tare weighed. The container is then filled a final weight which is a total weight of the liquid and the container. In a filling operation on an assembly line, the total weight of the liquid and container is variable since the weight of the individual container varies. To accommodate the variable weight of the filled container, automatic liquid filling on a weight basis requires an extremely complex apparatus. Typical apparatuses for filling containers by weight are disclosed in U.S. Pat. No. 3,100,584, U.S. Pat. No. 3,162,258 and U.S. Pat. No. 3,335,807.
Attempts have been made to provide a means for dispensing a predetermined weight of liquid by volumetric measurement by compensating for the change in temperature of the liquid by changing the volume of the container in response to the temperature of the liquid. Apparatuses as disclosed in U.S. Pat. No. 2,044,866 and U.S. Pat. No. 2,063,892 are typical. The apparatuses do not dispense a predetermined weight of material with accuracy since they attempt to control a level over a large cross section. Small inaccuracies in the temperature compensation or level control result in large errors in the weight of materials dispensed.
It is an object of the present invention to provide an apparatus for accurately dispensing a predetermined weight of a liquid. It is a further object of the present invention to provide an apparatus for dispensing a predetermined weight of a liquid by volumetric means. It is a further object of the present invention to provide an apparatus for accurately dispensing a predetermined weight of liquid over a broad temperature range.